Several problems should be paid attention to in compound fertilizer granulation

First, the humidity problem: the optimum moisture content of urea ammonium phosphate material is about 3%, which is lower than that of other systems, and the granulation qualification rate is only 30%, and the production capacity is low.

Second, the temperature problem: When the granulation temperature is high, the liquid phase of the system increases, because the inorganic salt increases with the increase of solubility, the mutual dissolution and reaction form the amount of double salt increases, the degree of uniformity increases, and the amount of liquid added It should be appropriately reduced, and the granulation moisture content should be adjusted as the solubility of the raw material changes.

Third, the problem of material solubility: In the high nitrogen ratio compound fertilizer manufacturing process, the amount of urea added is more than 50%, the solubility is large, and so the liquid amount is very high. It can be improved by adding powdered urea at lower operating temperatures. However, the urea dissolution and heat absorption operation reduces the granulation temperature and increases the difficulty of operation. The resulting low melting point mixture makes it more difficult to control the granulation.

Fourth, the material return problem: mainly affect the granulation temperature, humidity material solubility and granulation core, the temperature stability of the return material, particle size distribution and temperature, humidity is essential for granulation, must be strictly controlled.

Fifth, the PH problem of the material: PH is an important indicator of whether the compatibility of the material system is suitable. In the granulation system of ammonium phosphate, the PH value of the material is controlled between 6.0 and 6.5.

Sixth, the melting point of the material on the viscosity problem: the melting point of the mixture is generally lower than the lowest melting point of each component, the co-melting point of urea, potassium chloride, monoammonium phosphate system is about 115 degrees, which is the viscosity temperature.The operating temperature inside the fertilizer granulator machine should be near this temperature.

Finally, the environmental impact problem: When the granulation temperature and humidity are different from the ambient temperature and humidity, the environmental impact becomes very important and must be adjusted. Because the operational flexibility of the fertilizer granulator machine depends on the adjustment range of factors such as granulation temperature and humidity. The granulation temperature should be controlled between the viscous temperature and the ambient temperature to maintain a proper temperature difference to ensure that the material does not excessively viscous and has a certain crystallization rate.